The deposition of hard substances on the surfaces of metallic or ceramic substrates is highly important in the manufacture of abrading, grinding and cutting tools. Among the known procedures are galvanic deposition, sintering of hard-substance dispersion on substrates or coating by means of an organic plastic.
The German AS No. 12 59 681 describes a procedure to join individual diamonds to metallic surfaces by brazing at 1100.degree. to 1300.degree. C. in vacuum or in an inert gas atmosphere using a binary or ternary solder of gold with 1 to 25% tantalum and/or 1 to 10% niobium. This procedure is comparatively labor intensive and requires costly gold solder.
The German AS No. 12 10 300 discloses a procedure wherein diamonds initially are immersed into a suspension of titanium powder and a solvent. After the volatile solvent has evaporated, the pre-coated diamonds are dipped into a melt of a silver-copper eutectic, the excess solder is removed and brazing then is carried out. This procedure is suitable to braze individual diamonds. Surface-coating with a fine-particulate dispersion of diamonds is impossible in this procedure.
The German OLS No. 24 11 785 discloses a procedure for the manufacture of grinding-tool surfaces by brazing diamond crystals which are not pre-coated on metal surfaces. The diamond crystals together with a powder of solder alloy and a binder are deposited on the surface and heated to about 1300.degree. C. The solder used is an alloy with at least 50% nickel and at least 5% chromium. However the high brazing temperatures may cause graphitization of the diamond powder and may render the substrates unsuitable. Furthermore, the chromium portions of the solder require a furnace atmosphere with a very low dew point.